Seam configuration for a flexible container

ABSTRACT

A seam configuration for a flexible container and a method for forming the seam configuration. The seam configuration includes a first hem having a first hem outer surface, a second hem having a second hem outer surface, and a primary seam which is formed by fusing together the first hem outer surface and the second hem outer surface. The method includes the steps of forming a first fold to create the first hem, forming a second fold to create the second hem, positioning the first hem outer surface and the second hem outer surface so that they are contiguous, and then fusing together the first hem outer surface and the second hem outer surface to form the primary seam.

TECHNICAL FIELD

[0001] A seam configuration for a flexible container and a method for forming the seam configuration.

BACKGROUND OF THE INVENTION

[0002] Flexible containers are commonly used for the handling, storage and transportation of flowable materials such as particulate substances in granular or powder form. Flexible containers are also referred to as “bulk containers”, “flexible intermediate bulk containers” or “FIBCs”. A flexible container may hold up to a tonne or more of a flowable material.

[0003] A flexible container typically consists of at least a continuous side wall and a bottom end wall. It may also include a top end wall. One or both of the end walls may also be fitted with a spout to facilitate either filling or emptying of the flexible container. The side wall of a flexible container may be formed from a tubular blank of material or may be formed from one or more panels of material which are joined together to create the continuous side wall.

[0004] A flexible container is typically made from a synthetic material such as polyethylene, polypropylene or some other polymer. The synthetic material may be in the form of a film material or may consist of a woven material formed by weaving together individual strands of synthetic material.

[0005] Typically the synthetic material is a woven material which is formed into panels or sheets which are joined together to create the flexible container. Usually these panels of synthetic woven material are joined together by stitching.

[0006] Woven material is generally preferred as a material for constructing flexible containers because it has relatively high strength in comparison with film materials and is relatively economical to produce and use. Stitching is generally preferred for use in creating seams in flexible containers because stitching provides a relatively strong connection between panels in comparison with techniques such as fusing (i.e., gluing, melting, soldering or welding).

[0007] Stitching is also preferred for use in creating seams in woven materials because it has been found that the use of fusing techniques with woven materials may result in the seam exhibiting a “zippering” effect in which the seam fails catastrophically in response to stresses exerted on the seam. A similar “zippering” effect can result where seams in film materials are created by stitching, thus making stitched seams generally unsuitable for use with film materials.

[0008] Flexible containers consisting of stitched panels are generally satisfactory for transporting and storing relatively coarse grained flowable materials. Such containers are, however, less suitable for transporting and storing more fine grained materials which are able to pass either through the stitch holes or through the woven material itself. The presence of stitch holes and the woven material itself may also facilitate the entry of contaminants such as insects, water and other liquids into the flexible container.

[0009] Where leakage out of or into a flexible container is a concern, a more “hygienic” design of flexible container may be called for. A challenge in fabricating flexible containers is to achieve a design which is both suitably hygienic and strong enough to contain large amounts of flowable material. This challenge is made more difficult because of the inherent limitations in the techniques used for creating seams in woven material and film material, as discussed above.

[0010] One option for preventing leakage from or into a stitched flexible container is to line the interior of the stitched flexible container with a liner.

[0011] A liner is usually constructed of a film which is made from a synthetic material such as polyethylene, polypropylene or some other polymer. The liner may be made from a continuous tubular blank of film or may be made from panels or sheets which are joined together. Panels of synthetic liner material are usually joined by fusing the panels together with heat or by some other method which does not require stitching, since stitching will introduce holes into the liner material and may also make the liner prone to a “zippering” effect.

[0012] The primary advantage of a lined flexible container is that the strength and durability of the flexible container is derived from the stitched woven material which forms the flexible container itself, while the hygienic properties of the flexible container are derived from the liner, which itself does not need to exhibit significant strength. In fact, although a flexible container is typically reusable, a liner is often used only once, with the result that typically the liner need only be strong and durable enough to withstand a single use of the flexible container.

[0013] One disadvantage of a lined flexible container is that although the presence of a liner may render a stitched flexible container more hygienic without compromising its strength and durability, it may also add considerable cost to the flexible container, particularly if the liner is replaced following each use of the flexible container.

[0014] A second option for at least minimizing leakage from or into a stitched flexible container is to coat the interior surfaces of a woven material with a sealant material in order to close off the interstices inherent in the woven material. The sealant material may be comprised of a film coating, a liquid coating, or any other material which will close off the interstices.

[0015] The primary advantage of using a coated woven material in a flexible container is that it can provide a relatively hygienic flexible container without the expense of a liner and the fabrication costs associated therewith.

[0016] One major disadvantage of a flexible container constructed of a coated woven material is that such containers are typically fabricated by stitching in order to provide the necessary strength for the container and the coating will not eliminate leakage at the stitch holes. As a result, flexible containers constructed of a coated woven material are not fully effective for eliminating leakage from or into the flexible container.

[0017] The best option currently available for creating a fully effective hygienic flexible container is therefore to combine a woven outer flexible container having stitched seams with an inner liner having fused seams.

[0018] The prior art includes numerous examples of technologies which are directed at optimizing the fabrication of either a flexible container or a liner. Some of these technologies are directed at minimizing fabrication costs by minimizing the number of panels which must be joined together to form either the flexible container or the liner. Some of these technologies describe seam configurations for flexible containers which are directed at ensuring the strength of a seam or ensuring the sealing of a seam.

[0019] France Patent Publication No. 2,634,468 A1 (Dafour) describes a flexible container which is formed from four identical panels of material and which is lined with a liner which is formed from a tubular blank of film material. Stitched seams at each of the four corners of the flexible container both join the panels of the flexible container and hold the liner in place within the flexible container. Welds are also provided in the liner adjacent to the locations where the liner is stitched to the flexible container, thus isolating the interior of the liner from the stitching which might otherwise cause leakage of the liner.

[0020] U.K. Patent Application No. 2,103,576 A (Nattrass) describes a seam configuration for a flexible container which is directed at accommodating a lifting loop. The seam configuration is formed by folding back and stitching a “terminal strip” in each of two panels to be joined such that the terminal strip forms an open ended edge pocket on each panel. The fold edges of the two panels are then stitched together in overlapping fashion.

[0021] U.S. Pat. No. 5,139,346 (Watanabe et al) and U.S. Pat. No. 5,181,900 (Watanabe et al) both describe a flexible container which is fabricated from four identical assembly sheets. Each of the four assembly sheets is constructed of a main sheet, an inlet sheet and an outlet sheet. A stitched hem is formed along the longitudinal edges of each assembly sheet. The assembly sheets are then stitched together along the stitched hem.

[0022] U.S. Pat. No. 5,618,254 (Derby), U.S. Pat. No. 5,746,862 (Derby), U.S. Pat. No. 5,759,144 (Derby) and U.S. Pat. No. 5,984,850 (Derby) each describe a liner for a flexible container which is fabricated using an automated process. In the automated process, a continuous web of gusseted liner material consisting of a polymeric film is advanced along a predetermined path where it is simultaneously cut and resealed by heated air using a fusing technique. The apparent purpose of the invention in Derby is to provide a relatively efficient process for fabricating liners for flexible containers.

[0023] U.S. Pat. No. 4,790,029 (LaFleur et al) and U.S. Pat. No. 4,798,572 (LaFleur et al) both describe a flexible container which is fabricated in an automated process which is similar in some respects to the process described in Derby. In LaFleur, an elongate web of flexible material is severed along a zig zag line having substantially straight segments defining the sides of an isosceles triangle. The triangle portions of the flexible material are then joined together to form seams either by stitching (in the case of a woven material) or by heat sealing (in the case of a film material).

[0024] None of these prior art references are directed at the potential for utilizing fusing techniques to create a seam in a woven material. Furthermore, none of these prior art references are directed at a hygienic flexible container which is constructed from a woven material but does not include an inner liner.

SUMMARY OF THE INVENTION

[0025] The present invention is directed at a seam configuration for a flexible container, which seam configuration comprises a first hem, a second hem and a fused primary seam. The present invention is also directed at a method for forming the seam configuration.

[0026] The seam configuration of the present invention utilizes the fused primary seam to eliminate one source of leakage from or into the flexible container. In a preferred embodiment, the flexible container can be constructed from a coated woven material in order to seal the interstices in the woven material and thus eliminate a second source of leakage from or into the flexible container.

[0027] In one method aspect, the invention is a method of forming a seam configuration in a flexible container, the seam configuration comprising a primary seam adjacent to a first peripheral edge and a second peripheral edge in a flexible material comprising the flexible container, the method comprising the following steps:

[0028] (a) forming a first fold in the flexible material adjacent to the first edge in order to create a first hem, wherein the first hem is comprised of a first hem outer surface and a first hem inner surface;

[0029] (b) forming a second fold in the flexible material adjacent to the second edge in order to create a second hem, wherein the second hem is comprised of a second hem outer surface and a second hem inner surface;

[0030] (c) positioning the first hem outer surface and the second hem outer surface so that they are contiguous; and

[0031] (d) fusing together the first hem outer surface and the second hem outer surface to form the primary seam.

[0032] In another aspect, the invention is a seam configuration for a flexible container, comprising:

[0033] (a) a first hem associated with a first peripheral edge in a flexible material comprising the flexible container, wherein the first hem has a first hem length and wherein the first hem is comprised of a first hem outer surface and a first hem inner surface;

[0034] (b) a second hem associated with a second peripheral edge in the flexible material, wherein the second hem has a second hem length and wherein the second hem is comprised of a second hem outer surface and a second hem inner surface; and

[0035] (c) a primary seam between the first hem outer surface and the second hem outer surface, wherein the primary seam has a primary seam length and wherein the primary seam is formed by fusing together the first hem outer surface and the second hem outer surface.

[0036] The term “fusing” as used herein includes any technique which is effective to provide a chemical or physical bond or connection between the first hem outer surface and the second hem outer surface without perforating the flexible material. For example, the fusing technique may include the use of an adhesive, the use of heat, or a combination of techniques.

[0037] The flexible material comprising the flexible container may be comprised of any material which is suitable for use in a flexible container and which is compatible with the fusing technique used for creating the primary seam. The flexible material may also be comprised of more than one material, in which case the different materials should also be compatible with each other.

[0038] For example, the flexible material may be comprised of a natural or synthetic woven material or film material. If the flexible material is a woven natural material derived from such organic materials as hemp (i.e., burlap), the fusing technique used to form the primary seam preferably utilizes a glue which is suitable for gluing the organic material, since it may not be possible effectively to fuse such materials through the application of heat.

[0039] Preferably the flexible material comprising the flexible container is a synthetic material comprising an organic polymer. Although any such organic polymer material which is suitable for use in a flexible container may be used, preferred organic polymers include polyethylene and polypropylene, both of which are conventionally used in the fabrication of flexible containers and are capable of being fused through the application of heat.

[0040] The flexible material may be comprised of a woven material or a film material. Preferably the flexible material is comprised of a woven material because of the superior strength characteristics of woven materials. Where leakage from or into the flexible container is a concern, the woven flexible material is preferably coated or impregnated with a sealant to seal the interstices in the woven material.

[0041] Any mechanism or technique for sealing the interstices in the woven material may be used. Preferably the interstices in the woven flexible material are sealed by coating the woven material with at least one layer of a film material as a sealant so that the flexible material is comprised of a layer of woven material and a layer of film material.

[0042] The flexible container may be of any shape and may be constructed from any number of panels of flexible material. Preferably the flexible container is constructed from four identical panels which are joined together along four seam configurations to form the flexible container so that it has a generally rectangular cross section. As a result, preferably each seam configuration connects a first panel of flexible material with a second panel of flexible material.

[0043] The flexible container may or may not be equipped with one or both of a fill spout and a discharge spout. Preferably the flexible container includes both a fill spout and a discharge spout. These spouts are preferably integrally formed with the four panels of flexible material making up the flexible container so that each seam configuration can be formed in a single plane, thus simplifying the fabrication process for the flexible container.

[0044] The first hem has a first hem length and the second hem has a second hem length. The hem lengths may be any length relative to the lengths of the peripheral edges, so long as the resulting seam is strong enough to withstand the stresses exerted upon it in service. Preferably, however, the first hem length is substantially equal to the length of the first peripheral edge and preferably the second hem length is substantially equal to the length of the second peripheral edge.

[0045] The formation of the first fold in the flexible material results in the first hem inner surface facing a first adjacent portion of the flexible material. Similarly, the formation of the second fold in the flexible material results in the second hem inner surface facing a second adjacent portion of the flexible material.

[0046] Preferably the first hem inner surface is connected with the first adjacent portion along the first hem length to form a first hem connection having a first hem connection length and preferably the second hem inner surface is connected with the second adjacent portion along the second hem length to form a second hem connection having a second hem connection length.

[0047] The hem connection lengths may be any length relative to the hem lengths. Preferably, however, the hem connection lengths are substantially equal to the hem lengths in order to maximize the strength of the seam configuration.

[0048] Although the hem connections may be formed in any manner, techniques which create perforations in the flexible material are preferably avoided. For example, stitching the hem connections will introduce holes into the flexible material which may cause leakage from or into the flexible container. As a result, the hem connections are preferably formed by fusing together the hem inner surfaces with the adjacent portions. Most preferably the hem connections are formed by performing a fusing step which is similar or identical to the fusing step which is used to form the primary seam.

[0049] The primary seam is formed by fusing together the first hem outer surface and the second hem outer surface. The purpose of the primary seam is twofold. First, the primary seam connects the panels which make up the flexible container. Second, the primary seam provides a sealing function which prevents leakage from or into the flexible container.

[0050] Where the flexible material is comprised of an organic polymer, the fusing step is preferably comprised of heating the flexible material so that fusing is effected through melting, soldering or welding.

[0051] The flexible material may be heated in any manner which will facilitate the fusing step. Preferably the fusing step is comprised of heating the flexible material with a stream of heated gas. More preferably the stream of heated gas is supplied by a nozzle. Most preferably the fusing step is comprised of inserting the nozzle between the first hem outer surface and the second hem outer surface and passing the heated gas through the nozzle.

[0052] The fusing step is preferably comprised of heating the flexible material along the first hem length and the second hem length to form the primary seam so that it has a primary seam length. In the preferred embodiment, the fusing step is comprised of moving the nozzle along the first hem length and the second hem length to form the primary seam so that it has a primary seam length.

[0053] The primary seam length may be any length relative to the hem lengths. Preferably the primary seam length is substantially equal to the hem lengths.

[0054] The flexible container defines both an interior container space and an exterior container space. As used herein, the term “interior container space” refers to the inside volume of the flexible container and the term “exterior container space” refers to the space outside of the flexible container. Flowable material will be contained within the interior container space.

[0055] The seam configuration may be oriented so that the first edge and the second edge are located either within or outside the interior container space. Similarly, the fusing step may be performed either from the interior container space or from the exterior container space.

[0056] Preferably the first edge and the second edge are located within the interior container space. Preferably the fusing step is performed from the exterior container space in order to simplify the fabrication of the flexible container.

[0057] The seam configuration may optionally be further comprised of a secondary seam connecting the first hem outer surface and the second hem outer surface. The purpose of the secondary seam is to reinforce the primary seam and thus enhance the strength of the seam configuration.

[0058] The secondary seam may be formed by any technique for creating a seam, including fusing techniques as well as riveting, stapling and stitching techniques. Preferably the secondary seam is formed so that the integrity of the primary seam is not compromised. In particular, the secondary seam should preferably not introduce perforations into the flexible container in locations which will enable leakage from or into the flexible container.

[0059] The secondary seam has a secondary seam length. Preferably the secondary seam is substantially parallel to the primary seam. The secondary seam may be any length relative to the primary seam. Preferably, however, the secondary seam length is substantially equal to the primary seam length so that the secondary seam can reinforce the primary seam along substantially the entire length of the primary seam.

[0060] Preferably, the secondary seam is comprised of stitching together the first adjacent portion, the first hem, the second hem and the second adjacent portion. Stitching is preferred for the secondary seam because of the superior strength characteristics of stitched seams in woven materials.

[0061] Stitching will, however, create stitch holes in the flexible material. As a result, preferably the primary seam extends further toward the interior container space than does the secondary seam, so that the fused primary seam will provide a seal or barrier between the interior container space and the secondary seam to prevent leakage from or into the flexible container through the stitch holes of the secondary seam.

[0062] In addition, preferably the hem connections are formed by fusing and extend further toward the interior container space than does the secondary seam, so that the fused hem connections also provide a seal or barrier between the interior container space and the secondary seam to prevent leakage from or into the flexible container through the stitch holes of the secondary seam.

[0063] In the preferred embodiment, the first hem connection length, the second hem connection length, the primary seam length and the secondary seam length are all substantially equal. In addition, in the preferred embodiment the first hem connection, the second hem connection, the primary seam and the secondary seam are substantially parallel to each other. This design provides a seam configuration having maximum strength characteristics while minimizing the potential for leakage from or into the flexible container through the seam configuration.

BRIEF DESCRIPTION OF DRAWINGS

[0064] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0065]FIG. 1 is a plan view of a panel of flexible material according to a preferred embodiment of the invention.

[0066]FIG. 2 is a transverse section view of the panel of flexible material of FIG. 1, taken along line 2-2 of FIG. 1.

[0067]FIG. 3 is a pictorial view of a flexible container constructed according to a preferred embodiment of the invention.

[0068]FIG. 4 is a transverse section view of the flexible container of FIG. 3, taken along line 4-4 of FIG. 3.

[0069]FIG. 5 is a detail section view of a seam configuration from FIG. 4, taken at location 5 of FIG. 4.

DETAILED DESCRIPTION

[0070] The present invention relates to a seam configuration for a flexible container and to a method for creating the seam configuration. The invention also relates to a flexible container which includes the seam configuration and to a method for fabricating the flexible container.

[0071] Referring to FIGS. 3 and 4, the invention is directed broadly at the construction of a flexible container (20). The flexible container (20) may be of any shape, may be constructed of any number of panels of material, and each of the panels making up the flexible container (20) may be of any shape as may be dictated by the specific design of the flexible container (20).

[0072] In the preferred embodiment the flexible material is comprised of woven polyethylene or woven polypropylene, but other flexible materials or combinations of flexible materials may be used. If the flexible container (20) is intended for use in circumstances where leakage from or into the flexible container (20) is a concern, the flexible material may further comprise a sealant for sealing the interstices in the woven material. The sealant is preferably comprised of coating the flexible material with at least one layer of film material so that the flexible material is comprised of a layer of woven material and a layer of film material.

[0073] Referring to FIG. 3, in the preferred embodiment the flexible container (20) has a generally rectangular cross-section and includes a side wall (22), a top end wall (24), a bottom end wall (26), a fill spout (28) and a discharge spout (30). Referring to FIGS. 3 and 4, the flexible container (20) is constructed of four identical panels (32,34,36,38) of a flexible material which are connected together using the seam configuration (40) of the invention.

[0074] Referring to FIGS. 1 and 2, representative panel (32) is comprised of a side wall portion (42), a top end wall portion (44), a bottom end wall portion (46), a fill spout portion (48) and a discharge spout portion (50).

[0075] It can be seen that the general shape of the flexible container (20) will be determined by the number of panels that are used to construct the flexible container (20) and by the relative dimensions of the side wall portion (32) of the panels. Other features of the flexible container (20), such as the existence and dimensions of the fill spout (28), the discharge spout (30) and the existence of the top end wall (24) are determined by the specific configuration of the individual panels (32,34,36,38).

[0076] For example, the fill spout portion (48) of the panel (32) may be omitted if the fill spout (28) is not required and the discharge spout portion (50) of the panel (32) may be omitted if the discharge spout (30) is not required. In addition, the top end wall portion (44) of the panel (32) may be omitted if the flexible container (20) is to be open at the top.

[0077] The panel (32) is defined longitudinally by side edges (52) which extend along the entire length of the panel (32) from the fill spout portion (48) to the discharge spout portion (50). The lengths and orientations of the side edges (52) through the various portions (42,44,46,48,50) of the panel (32) will determine many of the features of the flexible container (20).

[0078] In the preferred embodiment, the side edges (52) are preferably substantially parallel to each other through the side wall portion (42) of the panel (32) so that the flexible container (20) has a substantially constant cross-section through the entire length of the side wall (22).

[0079] Through both the top end wall portion (44) of the panel (32) and the bottom end wall portion (46) of the panel (32) the side edges (52) each deflect obliquely so that they converge at an angle of about 90 degrees relative to each other. This configuration facilitates the connection of the top end wall portion (44) of the four panels (32,34,36,38) to form the top end wall (24) of the flexible container (20) and facilitates the connection of the bottom end wall portion (46) of the four panels (32,34,36,38) to form the bottom end wall (26) of the flexible container (20).

[0080] Through both the fill spout portion (48) of the panel (32) and the discharge spout portion (50) of the panel (32) the side edges (52) are preferably substantially parallel to each other so that the fill spout (28) and the discharge spout (30) have a substantially constant cross-section throughout their entire length. Alternatively, if either a tapered or flared fill spout (28) or discharge spout (30) is desired, the side edges (52) may be configured not to be parallel through either or both of the fill spout portion (48) or the discharge spout portion (50), as the case may be.

[0081] If the fill spout (28) is to be omitted from the flexible container (20), the side edges (52) may converge to a point through the top end wall portion (44) of the panel (32). Similarly, if the discharge spout (30) is to be omitted from the flexible container (20), the side edges (52) may converge to a point through the bottom end wall portion (46) of the panel (32).

[0082] Referring to FIGS. 1-5, the seam configuration (40) connects each of the four panels (32,34,36,38) together along substantially the entire length of the side edges (52) to form the flexible container (20). In the preferred embodiment four separate and identical seam configurations (40) are utilized to construct the flexible container. Each seam configuration (40) in the preferred embodiment is a combination of a hem, a primary seam and a secondary seam.

[0083] Referring to FIGS. 1 to 5, each panel (32,34,36,38) is further comprised of peripheral edges (54). Referring to FIG. 1, to prepare the panel (32) for creation of the seam configuration (40), a hem (56) is created adjacent to each of the peripheral edges (54) by forming a fold in the flexible material adjacent to the peripheral edge (54) and coincident with the side edge (52). In order to create a smooth hem (56), it may be necessary to cut the flexible material at locations where the side edges (52) changes direction in order to avoid gathering up of flexible material at such locations.

[0084] Each hem (56) is comprised of a hem outer surface (58) and a hem inner surface (60). The hem inner surface (60) faces an adjacent portion (62) of the flexible material. Each hem (56) has a hem length which is substantially equal to the length of its associated peripheral edge (54).

[0085] The hem inner surface (60) is connected with the adjacent portion (62) of the flexible material to form a hem connection (64). The hem connections (64) may be formed using any technique for forming seams, including riveting, stapling, welding and fusing techniques.

[0086] In the preferred embodiment, the hem connection (64) is formed by performing a fusing step to fuse together the hem inner surface (60) and the adjacent portion (62) to avoid creating perforations in the flexible material.

[0087] In the preferred embodiment this fusing step is performed by heating the flexible material with a stream of heated gas supplied by a nozzle and moving the nozzle along the length of the panel (32) to form each hem connection (64) so that it has a hem connection length which is substantially equal to the length of its associated hem (56).

[0088] Referring to FIGS. 4 and 5, in the preferred embodiment the next step in the creation of the seam configuration (40) is the formation of a primary seam (66) which is adjacent to a first peripheral edge (68) on one of the panels (32,34,36,38) and a second peripheral edge (70) on another of the panels (32,34,36,38) so that two of the panels (32,34,36,38) can be connected by the seam configuration (40).

[0089] Each primary seam (66) is formed by positioning a first hem outer surface (72) on one of the panels (32,34,36,38) and a second hem outer surface (74) on another of the panels (32,34,36,38) so that they are contiguous, and then fusing together the first hem outer surface (72) and the second hem outer surface (74).

[0090] In the preferred embodiment, each primary seam (66) is formed by a fusing step which is performed by heating the flexible material with a stream of heated gas supplied by a nozzle and moving the nozzle along the length of the adjacent panels (32,34,36,38) to form each primary seam (66) so that it has a primary seam length which is substantially equal to the length of its associated hems (56) and hem connections (64).

[0091] Referring to FIG. 4, in the preferred embodiment, each primary seam (66) is formed so that the peripheral edges (68,70) of the panels (32,34,36,38) are located within an interior container space (76) which is defined by the flexible container (20). It is believed that this configuration may provide greater strength for the primary seam (66) in comparison with a reverse configuration in which the peripheral edges (68,70) are located outside of the interior container space (76).

[0092] In addition, in the preferred embodiment, the fusing step for forming the primary seam (66) is performed from an exterior container space (78) which is defined by the flexible container (20). Performing the fusing step in this manner may simplify the fabrication of the flexible container (20) and may be easier to automate than if the fusing step is performed from within the interior container space (76).

[0093] If the flexible container (20) is intended for use in circumstances where leakage from or into the flexible container (20) is not a concern, the hem connections (64) and the primary seam (66) may be formed by stitching or by other techniques which may perforate the flexible material.

[0094] If the flexible container (20) is intended for use in circumstances where very high stresses are likely to be experienced by the seam configuration (40), each seam configuration (40) may optionally include a secondary seam (80) for connecting the first hem outer surface (72) and the second hem outer surface (74). The secondary seam (80) may be formed using any technique for forming seams, including riveting, stapling, stitching and fusing techniques.

[0095] Referring to FIGS. 4 and 5, in the preferred embodiment the secondary seam (80) is formed by stitching together the hems (56) and adjacent portions (62) of flexible material which are adjacent to the seam configuration (40). One or more rows of stitching may be used to form the secondary seam (80). Stitching is preferred for the secondary seam (80) because of the superior strength characteristics of stitched seams in woven materials.

[0096] Since stitching will perforate the flexible material, both the primary seam (66) and the hem connections (64) should extend further toward the interior container space (76) than does the secondary seam (80) if leakage from or into the flexible container (20) is a concern. This will ensure that the primary seam (66) and the hem connections (64) effectively “seal” the interior container space (76) from the perforations in the flexible material which are created by the secondary seam (80). This will also make it possible for the secondary seam (80) to be formed from the exterior container space (78), which may simplify the fabrication of the flexible container (20) and readily facilitate automation of the fabrication process.

[0097] In the preferred embodiment, each secondary seam (80) has a secondary seam length which is substantially equal to the length of its associated hems (56), hem connections (64) and primary seam (66). In addition, in the preferred embodiment the hem connections (64), the primary seam (66) and the secondary seam (80) associated with each seam configuration (40) are substantially parallel to each other.

[0098] The seam configuration (40) of the invention is particularly suited for use in constructing flexible containers which are fabricated from woven synthetic polymer materials such as polyethylene and polypropylene.

[0099] The seam configuration (40) facilitates the use of fusing techniques to form the primary seam (66) instead of techniques such as riveting, stapling and stitching, all of which introduce perforations into the flexible material. It has been found that the seam configuration (40) of the invention has reduced tendency to exhibit the “zippering” effect which is commonly experienced when fused seams are used with woven materials.

[0100] The reason for this phenomenon is not completely understood, but it is theorized that forming the primary seam (66) between the hem outer surfaces (72,74) has the effect of isolating the primary seam (66) from some of the stresses that are experienced by the flexible material when the flexible container (20) is in service. It is believed that this effect may be due to a combination of the configuration of the hems (56) and the location of the primary seam (66) relative to the hems (56).

[0101] The seam configuration (40) of the invention provides several advantages over conventional seams for flexible containers (20).

[0102] First, the seam configuration (40) of the preferred embodiment does not introduce perforations into the flexible material in locations where the perforations can communicate with the interior container space (76). This advantage is made possible through the use of fusing techniques for forming the hem connections (64) and the primary seam (66).

[0103] When this advantage is combined with the use of woven flexible materials which comprise a sealant, the result is a flexible container (20) which is relatively hygienic and does not permit leakage from or into the flexible container (20).

[0104] Second, because the seam configuration (40) utilizes fusing techniques for formation of the hem connections (64) and the primary seam (66), it offers the potential for reduced fabrication costs and increased potential for automation of the fabrication process, since fused connections and seams can potentially be formed for lower cost than those formed using riveting, stapling or stitching techniques.

[0105] When this advantage is combined with the use of four or fewer identical panels for the fabrication of the flexible container (20), which panels include a side wall portion (42), a top end wall portion (44), a bottom end wall portion (46), a fill spout portion (48) and a discharge spout portion (50), further reduced fabrication costs and further increased potential for automation of the fabrication process may result.

[0106] In particular, by providing that the flexible container (20) may be fabricated simply by forming seam configurations (40) between side edges (52) of adjacent panels (32,34,36,38), each seam configuration (40) may be formed in a single plane. This has the potential for further simplifying automated fabrication processes by limiting to two dimensions the motions that must be performed in forming the seam configurations (40) in comparison with some conventional fabrication methods which require the fill spout (28) and the discharge spout (30) to be fastened to the flexible container (20) in a process separate from the fabrication of the flexible container (20).

[0107] Third, the seam configuration of the present invention facilitates the addition of the optional secondary seam (80) which can be formed by riveting, stapling or stitching techniques to enhance the strength of the seam configuration (40) without compromising the hygienic properties provided by the fused hem connections (64) and fused primary seam (66). 

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A method of forming a seam configuration in a flexible container, the seam configuration comprising a primary seam adjacent to a first peripheral edge and a second peripheral edge in a flexible material comprising the flexible container, the method comprising the following steps: (a) forming a first fold in the flexible material adjacent to the first edge in order to create a first hem, wherein the first hem is comprised of a first hem outer surface and a first hem inner surface; (b) forming a second fold in the flexible material adjacent to the second edge in order to create a second hem, wherein the second hem is comprised of a second hem outer surface and a second hem inner surface; (c) positioning the first hem outer surface and the second hem outer surface so that they are contiguous; and (d) fusing together the first hem outer surface and the second hem outer surface to form the primary seam.
 2. The method as claimed in claim 1 wherein the flexible material is comprised of an organic polymer and wherein the fusing step is comprised of heating the flexible material to fuse together the first hem outer surface and the second hem outer surface.
 3. The method as claimed in claim 2 wherein the flexible container defines an interior container space and wherein the positioning step is performed such that the first edge and the second edge are both located within the interior container space.
 4. The method as claimed in claim 3 wherein the fusing step is comprised of heating the flexible material with a stream of heated gas.
 5. The method as claimed in claim 4 wherein the stream of heated gas is supplied by a nozzle.
 6. The method as claimed in claim 5 wherein the fusing step is comprised of inserting the nozzle between the first hem outer surface and the second hem outer surface and passing the heated gas through the nozzle.
 7. The method as claimed in claim 6 wherein the first hem has a first hem length, wherein the second hem has a second hem length, and wherein the fusing step is further comprised of moving the nozzle along the first hem length and the second hem length to form the primary seam such that the primary seam has a primary seam length.
 8. The method as claimed in claim 3 wherein the flexible material is comprised of a woven material.
 9. The method as claimed in claim 8 wherein the woven material includes a plurality of interstices and wherein the flexible material further comprises a sealant for sealing the interstices in the flexible material.
 10. The method as claimed in claim 9 wherein the flexible container defines an exterior container space and wherein the fusing step is performed from the exterior container space.
 11. The method as claimed in claim 3 wherein the first hem has a first hem length, wherein the second hem has a second hem length, and wherein the fusing step is comprised of heating the flexible material along the first hem length and the second hem length to form the primary seam such that the primary seam has a primary seam length.
 12. The method as claimed in claim 11 wherein the first hem inner surface faces a first adjacent portion of the flexible material and wherein the second hem inner surface faces a second adjacent portion of the flexible material, further comprising the step of fusing together the first hem inner surface and the first adjacent portion of the flexible material along the first hem length to form a first hem connection having a first hem connection length and further comprising the step of fusing together the second hem inner surface and the second adjacent portion of the flexible material along the second hem length to form a second hem connection having a second hem connection length.
 13. The method as claimed in claim 12 wherein the flexible container defines an interior container space, further comprising the step of forming a secondary seam connecting the first hem outer surface and the second hem outer surface, wherein the secondary seam has a secondary seam length and wherein the primary seam extends further toward the interior container space than does the secondary seam.
 14. The method as claimed in claim 13 wherein the first hem connection extends further toward the interior container space than does the secondary seam and wherein the second hem connection extends further toward the interior container space than does the secondary seam.
 15. The method as claimed in claim 14 wherein the secondary seam forming step is comprised of stitching together the first adjacent portion, the first hem, the second hem and the second adjacent portion.
 16. The method as claimed in claim 15 wherein the first hem connection, the second hem connection, the primary seam and the secondary seam are substantially parallel to each other.
 17. The method as claimed in claim 16 wherein the first hem connection length, the second hem connection length, the primary seam length and the secondary seam length are substantially equal.
 18. The method as claimed in claim 3 wherein the first edge is located on a first panel of the flexible material, wherein the second edge is located on a second panel of the flexible material, and wherein the primary seam connects the first panel and the second panel.
 19. A seam configuration for a flexible container, comprising: (a) a first hem associated with a first peripheral edge in a flexible material comprising the flexible container, wherein the first hem has a first hem length and wherein the first hem is comprised of a first hem outer surface and a first hem inner surface; (b) a second hem associated with a second peripheral edge in the flexible material, wherein the second hem has a second hem length and wherein the second hem is comprised of a second hem outer surface and a second hem inner surface; and (c) a primary seam between the first hem outer surface and the second hem outer surface, wherein the primary seam has a primary seam length and wherein the primary seam is formed by fusing together the first hem outer surface and the second hem outer surface.
 20. The seam configuration as claimed in claim 19 wherein the flexible material is comprised of an organic polymer.
 21. The seam configuration as claimed in claim 20 wherein the flexible container defines an interior container space and wherein the first edge and the second edge are both located within the interior container space.
 22. The seam configuration as claimed in claim 21 wherein the flexible material is comprised of a woven material.
 23. The seam configuration as claimed in claim 22 wherein the woven material includes a plurality of interstices and wherein the flexible material further comprises a sealant for sealing the interstices in the flexible material.
 24. The seam configuration as claimed in claim 21 wherein the first hem inner surface faces a first adjacent portion of the material, wherein the second hem inner surface faces a second adjacent portion of the material, wherein the first hem inner surface and the first adjacent portion are fused together to form a first hem connection having a first hem connection length, and wherein the second hem inner surface and the second adjacent portion are fused together to form a second hem connection having a second hem connection length.
 25. The seam configuration as claimed in claim 24 wherein the flexible container defines an interior container space, further comprising a secondary seam connecting the first hem outer surface and the second hem outer surface, wherein the secondary seam has a secondary seam length and wherein the primary seam extends further toward the interior container space than does the secondary seam.
 26. The seam configuration as claimed in claim 25 wherein the first hem connection extends further toward the interior container space than does the secondary seam and wherein the second hem connection extends further toward the interior container space than does the secondary seam.
 27. The seam configuration as claimed in claim 26 wherein the secondary seam is comprised of stitches passing through the first adjacent portion, the first hem, the second hem and the second adjacent portion.
 28. The seam configuration as claimed in claim 27 wherein the first hem connection, the second hem connection, the primary seam and the secondary seam are substantially parallel.
 29. The seam configuration as claimed in claim 28 wherein the first hem connection length, the second hem connection length, the primary seam length and the secondary seam length are substantially equal.
 30. The seam configuration as claimed in claim 21 wherein the first edge is located on a first panel of the flexible material, wherein the second edge is located on a second panel of the flexible material, and wherein the primary seam connects the first panel and the second panel. 